NPC Scan download link:
http://www.curse.com/addons/wow/npcscan
http://www.curse.com/addons/wow/npcscan-overlay
(Give you a nice little alert when NPC's in the area spawn)

IN CASE HE IS CACHED ON NPC SCAN!
World of Warcraft » Cache » WDB » EnGb (Right click your WoW icon and click open folder to get into your WoW folder)
In your enGB folder delete 'Npccache.wdb' and 'Creaturecashe.wdb'